(A and B) Semilogarithmic phase diagrams under increasing (blue) and decreasing (red) rainfall for (A) model with no termite mounds and (B) the modified model with 50% on- versus off-mound improvement in both growth rate and infiltration efficiency. (A) Without mounds, one hysteresis cycle occurs (i), corresponding to sudden transitions to and from desertification. (B) Adding mounds generates two hysteresis cycles, corresponding to loss/recovery of matrix vegetation (i) and desertification/revegetation (ii). For both (A) and (B), we used fixed rainfall rates and parameters as described in table S1 and fig. S5.

Images, Video, and Other Other Media

Sequence of snapshots obtained with the modified model with one mound, stochastic
rainfall rate, and parameterization as in Fig. 2. The red solid circle in the rainfall
function panel represents the actual value of R(t), whereas the mean value is given
by the brown curve. This movies shows the whole mound and surroundings (~20m lateral
size). Note that, with this dynamic rainfall function, there is a realistic delay
between the rainfall rate and the effects on the vegetation; thus, only well into
the dry season the system loses most of its vegetation, which resists on the mound
and as underground biomass. Once the rain season is well underway, vegetation is regenerated
in the whole ecosystem, with patterns that change as water availability changes.

Sequence of snapshots obtained with the modified model with one mound, stochastic
rainfall rate, and parameterization as in Fig. 2. The zoom is at 2m×2m, as in Fig.
2E. The red solid circle in the rainfall function panel represents the actual value
of R(t), whereas the mean value is given by the brown curve. This movie shows a zoom
of the area close to the mound boundaries.